class_docstr: Test cases for "small data" conversion and I/O.
code: def pdf(self):
      return pd.DataFrame(
          {"a": [1, 2, 3], "b": [4, 5, 6]}, index=[0, 1, 3]
      )
  
imports: import os
  import string
  import unittest
  import sys
  import numpy
  import pandas
  from pyspark import pandas
  from pyspark.testing.pandasutils import PandasOnSparkTestCase, TestUtils
  from pyspark.testing.sqlutils import SQLTestUtils
label_desc: Use image node_id 1 for calling the DataFrameConversionMixin obj's underlying member method code with example usage: obj.pdf() and returns: pd